Phase diagram of the Hubbard-Kondo lattice model from the variational cluster approximation

Abstract

The interplay between the Kondo effect and magnetic ordering driven by the Ruderman-Kittel-Kasuya-Yosida interaction is studied within the two-dimensional Hubbard-Kondo lattice model. In addition to the antiferromagnetic exchange interaction, J ⊥ , between the localized and the conduction electrons, this model also contains the local repulsion, U, between the conduction electrons. We use variational cluster approximation to investigate the competition between the antiferromagnetic phase, the Kondo singlet phase, and a ferrimagnetic phase on square lattice. At half-filling, the Néel antiferromagnetic phase dominates from small to moderate J ⊥ and UJ ⊥ , and the Kondo singlet elsewhere. Sufficiently away from half-filling, the antiferromagnetic phase first gives way to a ferrimagnetic phase (in which the localized spins order ferromagnetically, and the conduction electrons do likewise, but the two mutually align antiferromagnetically), and then to the Kondo singlet phase. arXiv:1804.00917v1 [cond-mat.str-el]

Spiral magnetism and chiral superconductivity in Kondo-Hubbard triangular lattice model

“…These values are compatibles to the parameters α ≈ 0.58t and β ≈ 4.26t found from square lattice in Ref. [1]. In Fig.…”

“…At half-filling, the ground state of the Kondo lattice model is an insulator. This can be explained by the formation of singlet between the conduction and impurity electrons or the presence of magnetic ordering of the impurity electrons via the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by itinerant electrons [1,[13][14][15][16][17]. The results obtained using mean field theory indicate an antiferromagnetic (AFM) and ferromagnetic (FM) phase order at halffilling and low doping respectively [18].…”

“…In addition to the antiferromagnetic exchange interaction J ⊥ between the conduction and impurity electrons, our model includes the local repulsion U of the conduction electrons, and the Heisenberg interaction J H between impurity electrons. Using the variational cluster approximation (VCA) [1,[41][42][43][44], an approach based on the rigorous variational principal which treats short-range correlation exactly, we obtain the quantum phase diagrams in both planes (J ⊥ , UJ ⊥ ) and (J ⊥ , J H ). We identify a long range, three-sublattice, spiral magnetic order which dominates the phase diagram for small J ⊥ and moderate U, while a Kondo singlet phase becomes more stable at large J ⊥ .…”

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Building on the results of Ref. [1], which identified an antiferromagnetic and Kondo singlet phases on the Kondo-Hubbard square lattice, we use the variational cluster approximation (VCA) to investigate the competition between these phases on a two-dimensional triangular lattice with 120 o spin orientation. In addition to the antiferromagnetic exchange interaction J ⊥ between the localized (impurity) and conduction (itinerant) electrons, our model includes the local repulsion U of the conduction electrons and the Heisenberg interaction J H between the impurities.

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Inversion and magnetic quantum oscillations in the symmetric periodic Anderson model

“…This contour, upon decreasing V , tends towards the boundary of the half Brillouin zone. The behaviour of the charge gap here is similar to what we had found for the KLM [10,32].…”